Diagnosis of HIV Infection in children

Transcription

1 Diagnosis of HIV Infection in children by Associate Professor Kulkanya Chokephaibulkit Department of Pediatrics, Faculty of Medicine Siriraj Hospital, Mahidol University.

2 Topic To Be Discussed WHO Testing Protocol Experiences with dry blood spot technique Entry points for testing immunization growth monitoring feeding center IMCI Informed consent for testing in children/minors Recommendation for resource-limited settings

3 Benefit of Making Early Diagnosis Efficiently monitor of PMTCT program - lead to improvement of the program Facilitate medical Rx, improve outcome - PCP prophylaxis - ARV Society & Mental benefit (especially for uninfected results) - Family make proper plan for the child and caretakers

4 Diagnosis of HIV Infection in Children In >18 months of age - diagnose by Anti-HIV serology In <18 months of age - Maternal antibody may persist up to 18 month-old old - Clinical symptoms can guide, but not reliable, and may overlap with other problems - Require detection of the virus to confirm infections - DNA-PCR - RNA-PCR - p24 Ag

5 WHO Recommendations Methods for Establishing HIV Infection in Infants and Children Method of diagnosis Virological methods HIV antibody testing Recommendations for use To diagnose infection in infants and children aged under 18 months; initial testing is recommended from 6 weeks of age To diagnose HIV infection in mother or identify HIV exposure of infant To diagnose HIV infection in children aged 18 months or more To identify HIV-antibody positive children aged under 18 months and support a presumptive clinical diagnosis of severe HIV disease to allow initiation of ART To exclude HIV infection where HIV antibody negative in children aged under 18 months who are HIV exposed and never breastfed To exclude HIV infection where HIV antibody negative in children aged under 18 months who are HIV exposed and discontinued breastfeeding for more than 6 weeks Strength of recommendation/level of evidence HIV DNA (A(I)) HIV RNA (A(I)) U p24 ag (CII) A (I) A (I) A (IV) A (I) A (IV)

6 Anti-HIV Serology Should be tested by 2 different HIV tests If negative (and asymptomatic) >>can exclude infection in any age - 74% of HIV-exposed uninfected infants sero-revert revert by 9 mo, and 96% by 12 mo. - Breast feeding may cause infection later >> Need to D C C BF >6 wk before excluding infection If Seronegative positive: result can be false in some advanced cases - Beyond 18 mo => confirm infection Do not use combi test, it may pos beyond 18 mo. - Younger than 18 mo =>unable to interpret

7 Seroconversion Sensitivity HIV combination Ag/Ab kits (4 th generation) HIVAb kits 3 rd generation Roche

8 Fourth generation Third generation No. Age Ab/Ag I Ab/Ag II Ax Vi PA 1 1 yo ND ND 3 1yo ND 4 1yo ND yo ND 6 1yo ND 8 1yo ND 9 17 mo th generation serologic test may be too sensitive to diagnose HIV infection in infants 18 mo Determine mo ND 7 1yo ND ND mo ND

9 Virological Tests (PCR for DNA / RNA, p24 Ag) Suggest to test at 6-8 wk of age - Repeat on a separate sample if possible, may be at 4 mo (US suggests : HIV is excluded if at least 2 negative PCR (at >1 mo, and > 4 mo) Caveat : Should confirm virological test with serology Some non-subtype B or group O can be false negative PCR (newer assays are better)

10 Special Situations Diagnosis in breast feeding infants >> Need to quit BF >6 wk before testing, as infection occur at any time via breast milk >> If quit > 6 wk, interpret the results as usual Negative serology in symptomatic infants >> Recheck with virological test Discrepant PCR result (+ -,, or - +) >> confirm with serology at mo.

11 WHO: Management of HIV Infection in Infants / Children

12 WHO: Management of HIV Infection in Infants / Children

13 Diagnosing HIV infection in infants and children less than18 months of age with unknown HIV exposure

14 Diagnosing HIV infection in infants and children less than 18 months of age with ongoing breastfeeding

15 Diagnosing HIV infection in infants and children less than 18 months of age with an initial negative HIV virological test and presenting with signs/symptoms of HIV at follow-up visit

16 Diagnosing HIV infection in infants and children aged 18 months or more

17 WHO Recommendations Methods for Establishing HIV Infection in Infants and Children < 18 mo Non breastfed child Breastfed child Diagnostic virological test from 6 week of age Negative test result Positive test result Negative test result Child is uninfected Child is infected Refer for HIV treatment and care including initiation of ART Children remains at risk of acquiring HIV infection until complete cessation of breastfeeding Child develops signs or symptoms suggestive of HIV Virology test available Virology test positive Diagnostic HIV testing (9-18 mo) Virology test not readily available HIV antibody test (18 mo) Child remains well Routine follow-up testing as per national programme recommendations (9-18 mo) Child is infected HIV antibody positive, Presumptive severe HIV disease Not breasted Refer for assessment for HIV treatment and care including initiation of ART Breasted

18 Does DNA-PCR Equal RNA-PCR? Most of the time RNA-PCR is as sensitive (90-100%) especially by mo, because all of perinatal infection have very high viral load by 2-32 month of age RNA-PCR may be undetectable from the effect of perinatal ART & neonatal prophylaxis, and may be, ART in breast milk p24 Ag may be affected by perinatal ART DNA-PCR is not affected by perinatal ART and ART in breast milk

19 Rate of Positivity in HIV-Infected Infants Age DNA-PCR RNA-PCR 2 weeks 38% 63% 4 weeks 71% 100% 7-88 weeks 100% 100%

20 Sensitivity and Specificity of RNA and DNA polymerase chain reaction (PCR) Age RNA-PCR 95% CI DNA-PCR 95% CI Sensitivity Birth 25/53 (47%) /53 (38%) months 47/47 (100%) /47 (100%) months 35/35 (100%) /35 (100%) Specificity Birth 100/100 (100%) (100%) months Not evaluated 325/325 (100%) months 100/100 (100%) /282 (100%) Young NL. JAID 2000;24:401-7.

21 Other Tests HIV-culture - Not better than PCR - Need facilities, more expensive, take longer time HIV-IgM IgM: : non-specific and cross react with RF HIV-IgA IgA: : not sensitive in younger than 6 mo. P24 Ag by Immune Complex Dissociation Assay - Highly specific but less sensitive (sens = 81%, spec = 100% at 15 d -33 mo) NEJM 1993;328:

22 Experiences With Dry Blood Spot Technique: Advantages Small volume required Ease of sample collection, storage and shipment Noninfectious transport medium Safety/ handling exposure Stability of sample stable in room T > 1 month Allows for centralization of testing facilities Facilitates systemic, unbiased surveillance

23 Experiences With Dry Blood Spot Technique: Limitations Live viral isolates can not be determined from DBS Sample processing is more difficult, require more steps Lymphocytes subsets can not be measured It is difficult to obtain long PCR fragment (>1.2 kb) DBS based genetic screening

24 Performance characteristics between whole blood and DBS for HIV-1 infant diagnosis and viral load monitoring Characteristics Stability of samples Sample collection Transportation of specimen Assay to be used Volume of blood sample required Whole blood DBS - Up to 4 days at ºC - Up to at least 3 months at room temperature - More difficult especially in infant age less than 1 year - Require cold chain storage to ensure specimen integrity - In-house or commercial kit - Standard procedure, less complexity - Easy to collect sample in young infant - Can be transport at room temperature but avoid from heat and humidity - In-house or commercial kit - Modified procedure, more complexity - At least 100µL - At least 10µL

25 FDA Approved Filter papers Whatman -BFC 180 Scheicher & Schuell - Grade 903

26 HIV-1 proviral DNA Detection in Whole Blood and DBS by Multiplex DNA-PCR (In house) and Commercial Standard Method Amplicor HIV-1 test Sample with known HIV status HIV-1 proviral DNA detection in : Positive (50 cases) Negative ( 30 cases) WB by Amplicor WB by Multiplex S&S IsoCode Whatman 47/50 (94%) 50/50 (100%) 50/50 (100%) 50/50 (100%) 42/47* (89.4%) 28/28** (100%) 47/50 (94%) 30/30 (100%) Sensitivity Specificity * Low DNA template 3 cases **Low DNA template 2 cases Uttayamakul S. J of Virological Methods 2005;128:

27 Prospective Field-Collected Dried Blood Spot DNA & RNA PCR for Infant Diagnosis and Viral load Monitoring of HIV-1 Infection in Thailand Young NL 1-2, Chokephaibulkit K 3, Chotpitayasunondh T 4, Chaowanachan T 1, Teeratkul A 1, Jetsawang B 1, Neeyapun K 1, Simonds RJ HIV/AIDS Collaboration, Nonthaburi, Thailand 2 CDC, Atlanta, GA, USA 3 Siriraj Hospital, Mahidol Univ., Bangkok, Thailand 4 Queen Sirirkit NICH, MOPH, Bangkok, Thailand : Poster Presentation at 6 th International Congress on AIDS in Asia and the Pacific, October 5-10, 2001; Melbourne, Australia : Oral Presentation in XIV International AIDS Conference, July 5-12, 2002; Barcelona, Spain

28 Specificity and sensitivity of DBS compared to venipuncture whole blood samples for diagnosis of HIV-1 infection Assay Amplicor DNA PCR a Biomerieux RNA NASBA b In-house real-time PCR c Positive Whole blood Negative Positive DBS Negative 56/56 106/106 56/56 106/106 56/56 106/106 56/56 106/106 Not done Not done 54/56 25/25 Sensitivity = %, specificity = 100% a whole blood samples assayed was white blood cell pellet b whole blood samples assayed was plasma c In the real-time PCR assay, only 25 negative samples were tested

29 Entry Points for Testing It is best to screen at well baby clinic that include: immunization growth monitoring feeding center Anticipatory guidance Educational activities Integrated management of childhood illness: Integrate preventive and curative intervention to improve practices both in health facilities and at home; aim against 5 common diseases: ARI, diarrhea, measles, malaria, and malnutrition

30 EDUCATIONAL CLASS NURSE STATION PLAY AREA

31 PHYSICAL EXAMINATION ROOM VACCINATION ROOM BLOOD COLLECTING ROOM

32 Informed Consent for Testing in Children / Minors Depend on local law In Thailand, under 18 years old require parental (or legal guardian, or caregiver s) consent, unless married Principal of Interest Balancing - In symptomatics: : to help with treatment - In asymptomatics,, esp. young children: to decide for ARV and PCP prophylaxis

33 Recommendation for Resource-Limited Settings Need to develop an easier, cheaper, and more practical test for early diagnosis. - Boosted p24 Ag assay? - Commercial by Perkin Elmer - Very promising, cheaper ($5( $5-10), but need more study and standardization - Sensitivity 100% if VL >30,000, 30,000, 46% if VL <30,000 ICM 2005;43:506-8, specificity >98% PIDJ 2004;23: Corporate HIV diagnosis into the one stop service for routine well child care Develop a specific national policy and guidelines Secure adequate supplies and resources

34 Boosted p24 Ag Correlate Well With HIV-RNA Sutthent R. J Clin Micro 2003;41(3): Brinkhof M WG. JAIDS 2006; 41: Boosted p24 Ag may be an alternative marker for treatment monitoring

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